Procedures and chemical compositions for the removal of color from synthetic polymer shapes such as fibers, yarns, fabrics or sheets are known in the prior art and are quite well documented. The most commonly used method for stripping dye from polymeric materials, such as polyester, is by treating such materials, near the boil, with an aqueous bath containing a bleaching agent, such as sodium chlorite, an acid and a dye carrier. The polyester materials are then thoroughly rinsed and given an antichlor treatment followed by a final aqueous rinse. Other methods use 1% to 2% aqueous emulsions of chlorinated or other organic solvents. However, with these procedures extreme difficulty is encountered in completely decolorizing the polymeric materials. Furthermore, processing time runs into several hours due to the requirement of a multiplicity of steps before and after the actual lengthy stripping stage. Invariably the final decolorized product is never totally white.
In another domain, polyester photographic or x-ray film bases are tinted or dyed in order to obtain various effects and in the particular case of x-ray films, to enhance the sharpness of the image. The exposed films are desilvered and the tinted film is then scrapped or disposed in land fills. It is therefore most desirable to reclaim the scrap by removing totally the residual tint and reusing it as film or other plastic products. However, present processes are based on solvent extractions, with the film remaining in contact with the solvent and under agitation for very lengthy periods of time without achieving total color removal. The use of organic solvents, processing time and special equipment make such stripping methods very expensive and not very successful.
Due to this lack of suitable processes for effectively and economically decolorizing synthetic polymeric materials to a totally white and color free product, textile items have to be reworked by cumbersome methods and x-ray film scrap never reaches a color free state suitable for effective reclamation. According to the process of this invention, polymeric materials that are colored with one or more dyestuffs can be rapidly and effectively decolorized by removing the coloring chemicals and producing a white, color-free product. Thus this invention overcomes many of the problems that are inherent in previously known decolorizing processes and in addition provides several advantages. The chemical systems of the present invention use relatively inexpensive and readily available chemicals which, when combined as taught below, generate synergistic chemical stripping compositions that rapidly and effectively remove all coloration from polymeric materials such as polyester in various shapes sch as film, yarn, fabrics or sheets. Further, the present invention does not require utilizing the extreme conditions necessary in some of the prior art methods that cause significant swelling, softening, or physical damage to the polymeric materials. Excellent stripping is achieved without the undesirable effects of possible polymer degradation and negative changes in physical performance properties.